42 



MORPHOLOGY AJSTD CULTURE OF MICROORGANISMS 



several nuclei. The yeast-forms of the Mucorinea, which are not other- 

 wise very typical forms, are always multihuclear. 



To whichever of these three structural forms a mold belongs, it 

 always represents some similar constitutional elements which we will 

 now consider. 



Cytoplasm. — The cytoplasm is a seini-fluid mass, somewhat dense, 



sometimes homogeneous and con- 

 taining a more or less considerable 

 number of vacuoles. Certain methods 

 of fixing and staining have recently 

 made possible a demonstration, in the 

 cytoplasm of the most diverse molds, 

 of the presence of a chondrium, very 

 clear and always splendidly exhibited. 

 This consists mostly of fine rod- 

 mitochondria, very long and flexible, 

 generally lying parallel with the 

 longitudinal axis of the cell (Fig. 25). 

 Sometimes also it contains granular 

 mitochondria. 



The cytoplasm also has reserve 

 products, of which, we shall speak 

 later. 



NucLKi. — The nuclei show a differ- 

 entiated structure which is sometimes 

 difficult to demonstrate. They con- 

 sist of a nuclear membrane, a hyaline 

 nucleoplasm, a large nucleolus and a 

 chromatic network. The last is some- 

 times indistinct, and it frequently 

 happens that the nucleus appears to 

 contain only a nucleolus; but a very 

 careful examination always reveals 

 the network (Fig. 24, 3 and 4). 

 The division of the nucleus is not always easy to observe. To study 

 it, one must examine the growing tips of the mycelium. In some cases 

 this consists in an elongation of the nucleus which soon assumes the 

 form of a very slender dumb-bell which breaks &.part at the narrow 



Fig. 25. — Various molds fixed 

 and stained by a special technic, 

 showing their chondrium. i, FHa,- 

 raentoi Rhizopus nigricans {Mucor). 

 2-4, Filaments of Penicillium glau- 

 cum. s ^'Hd 6> Fragments of the 

 conidial organ of the same mold. 

 7, Filam^ent of Endomyces magnusii. 

 8 and 9, Oidia of the same mold. 

 In all these molds, chondrium is 

 represented by long filaments, or 

 sometimes by small grains. The 

 filaments often show small vesicles 

 at their crossing. 



